Eucalyptus leaf is antibacterial, antiseptic, and astringent. It was most likely first used by the Aborigines of Australia, who applied it as a poultice for wounds, abscesses, and fungal infections of the skin. They also drank eucalyptus leaf tea to reduce fevers. In 19th century England, eucalyptus oil was used in hospitals to clean urinary catheters. Today, herbalists use fresh leaves as a topical antiseptic for wounds and recommend eucalyptus gargles for sore throats, as well as inhalation of the essential oil vapors for the treatment of croup, bronchitis, asthma, nasal congestion, and flu. The oil is antiviral and expectorant; eucalyptus oil-based chest rubs and vapor inhalations relieve respiratory ailments.

Eucalyptus is added to perfumes, soaps, foods, and beverages. It's also found in wax candles and topical sprays to repel insects. Recent research suggests that washing bedclothes with eucalyptus oil may decrease asthmatic patients' exposure to dust mites. Its effects on insect habitats gave it the nickname Australian fevertree: eucalyptus trees dried marshes in which it was planted, so that malaria-bearing mosquitos could not proliferate. It also kills cockroaches. Eucalyptus oil is highly toxic to humans and should be used with care.

There are over 500 species of eucalyptus plants, ranging in height from five-foot shrubs to 480-foot trees. Of these, blue gum is the most common. Reaching up to 230 feet in height, it has smooth, blue-gray bark that peels in shreds, revealing a cream-colored trunk beneath.

Young leaves are opposite and broad; mature 4- to 12-inch leaves are alternate, swordlike, thick, dark green, and shiny. Clusters of flowers grow near axils, bear no petals but white flower stamens, and give way to seeded fruits. The roots, which collect water, quench thirst. When one end of a root is blown into, water drips out the other end and can be collected in a vessel. Eucalyptus is native to Australia and cultivated in Europe, the United States, China, Africa, and South America. The leaves and branch tips are the source of crude extracts and steam-distilled oil.

• Leaves
• Branch tips

Fresh and dried leaves and branch tips yield yellow, sometimes colorless, volatile oil which consists primarily of cineole (70% to 85%; formerly called eucalyptol); also, monoterpenes (borneol, terpenines, a-terpineol, citronellal, geraniol, iso-fenchone, limonene, linalool, myrcene, a-phellandrene, a- and b-pinene, camphene, trans-pinocarveol, piperitone); sesquiterpenes (aromadendrene, cadinene, caryophyllene, a-copaene, a-,b-, and gamma-eudesmol, globulol); alkanes; flavonoids (eucalyptin). Leaf contains tannins, flavonoids (procyanidin b-2,3'-O-galloyl, prodelphinidin b-2,3'-O-galloyl, prodelphinidin, quercetin, hyperoside, rutin).

Liquid essential oil (dilute with water, oil, or rubbing alcohol before using), topical creams containing essential oil. To be used commercially, eucalyptus oil must have a high percentage of cineole (not less than 70%). Concentrations of phellandrene and aldehydes must be low. Crude leaf and aqueous extracts from leaf material are also available.

Commercial cough drops, syrups, vaporizer fluid, liniments, toothpaste, and mouthwash may contain eucalyptus oil or 1.8-cineole; both are also used in dentistry. Used in perfume, no more than 1.0% oil is allowed in products; 0.002% is the allowable limit for 1.8-cineole content in foods.

Traditional actions: oil—antiseptic, expectorant, antiviral, febrifuge; leaves—decongestant, astringent, stimulant. Eucalyptus was historically used for pulmonary tuberculosis, bacterial dysentery, and aching joints, but it is no longer used clinically for these conditions.

Eucalyptus leaves are currently used internally for bronchial and throat inflammation, excess mucus, congestive chest conditions, to combat colds and influenza. Eucalyptus oil is used externally for chest congestion, aches and pains, ringworm, tinnea, and as a deodorant.

Clinical applications: The German Commission E approves internal use of leaf extracts and steam inhalation of essential oil for catarrh of the upper respiratory tract, and dilute essential oil topical applications to relieve rheumatic discomfort.

Essential oil is antibacterial against Escherichia coli, Staphylococcus species, Pseudomonas, Enterobacter species, Hemophilus influenzae, Proteus mirabilis, and Klebsiella species in agar plate tests. It is antifungal to Trichoderma viride. Gram-positive bacteria are apparently the most sensitive to eucalyptus preparations. Oral doses and external application are expectorant.

Crude leaf extract lowers high blood sugar levels in rabbits. The flavonoids quercetin and hyperoside demonstrate in vitro anti-influenza (Type A) activity.

In humans, a combination formula including eucalyptus oil has been used to successfully treat suppurative otitis. Topical application inhibits prostaglandin synthesis, and stimulates mild hyperemic, expectorant, and secretolytic effects. Leaf extracts stimulate the same effects.

• Eucalyptus leaf as infusion: 1 to 2 g per cup tid
• Eucalyptus leaf tincture (for catarrh): 0.5 to 1 ml/day
• Oil for topical application (sore joints or chest rub for catarrh): 30 ml oil to 500 ml lukewarm water.
• Eucalyptol (catarrh): 0.05 to 0.2 ml (1 to 2 drops per cup boiling water) daily
• Eucalyptus oil (for topical application): add 0.5 to 1 ml (15 to 30 drops) of oil to 1/2 cup of carrier oil (sesame, olive, etc.). For inhalation, add 5 to 10 drops of oil to 2 cups boiling water; place towel over head and inhale steam.

When used externally, eucalyptus oil is nontoxic, nonsensitizing, and does not promote phototoxicity. Internally, eucalyptus oil is toxic and must be diluted. Ingestion of 3.4 ml oil has resulted in death.

The American Herbal Products Association gives eucalyptus leaf a class 2d safety rating, specifying gastric and bile duct inflammatory disease as contraindications, and cautioning against use on the faces of children under age 2. Tannins (comprising 11% of leaf extract constituents) in the leaves may cause gastrointestinal distress or kidney and liver damage if leaf preparations are ingested in large amounts.

Symptoms of poisoning include epigastric burning, miosis, cyanosis, and convulsions. Charcoal lavage, diazepam, atropine, electrolyte replenishment, sodium bicarbonate, intubation, or oxygen respiration may be required as treatments. Nonfatal doses of leaf extracts or essential oil caused nausea, vomiting, diarrhea.

Eucalyptus oil should not be ingested; should be in diluted form when used topically. Do not use while pregnant or breast-feeding. Not for use in patients with inflammatory disease of gastrointestinal tract or bile ducts, or severe liver disease. Eucalyptus oil should not be applied to the face of infants or young children, and especially not near the nose or mouth; glottal spasm, bronchial spasm, or asphyxiation may result.

In a study evaluating potential essential oils as transdermal delivery agents, eucalyptus oil acted as a penetration enhancer for 5-fluorouracil (5-FU) using excised rat skin (Abdullah et al. 1996). Eucalyptus oil was the most active essential oil studied and enhanced the permeation of 5-fluorouracil approximately 60-fold. The mechanism for the accelerated percutaneous absorption of 5-FU combined with these essential oils may be due to a combination of partition and diffusion.

Approved for food use in appropriate quantities in the U.S., and also as a dietary supplement. Licensed through the General Sale List in England. Approved for the treatment of respiratory catarrh and rheumatic complaints by the German Commission E.

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